Many research efforts have reported using iron-based materials to manufacture a biological absorbable and implantable medical device. Compared with magnesium-based materials and degradable polymers, an implantable medical device is made of the iron-based alloy which has more ideal strength and slower absorption speed. For example, an iron-based alloy intraluminal scaffold can provide enough effective support during the healing stage of the lumen tissue (for example, the healing stage of vessel is about 3 months). However, there is a drawback of iron-based intraluminal scaffold that after the lumen tissue is repaired, the iron-based intraluminal scaffold corrodes slowly and does not completely corrode in the short-term. Therefore, the clinical degradation time requirement for an absorbable device cannot be satisfied, so the iron corrosion speed needs to be improved.
The prior art discloses that an iron-based substrate with degradable polyester coating on its surface can improve the corrosion speed of the iron-based alloy. The corrosion speed of iron-based material is demonstrated to significantly improve by accelerating its corrosion in a local subacidic environment near the implantation location of the device resulting from the degradation of a degradable polyester, which decreases the pH of local environment. Corrosion products of an iron-based material were obtained when the iron-based material corroded.
Whether the mass of the iron-based materials matches the mass of the degradable polyester coat affects the corrosion speed of the iron-based material and the final corrosion product morphology. For a given specification iron-based device, when the degradable polyester type and mass of the degradable polyester that is sufficient to completely corrode the iron-based substrate are determined, whether the degradation speed of the degradable polyester matches the corrosion speed of the iron-based alloy affects the early mechanical performance of the implantable device. For example, local corrosion may easily occur in the iron-based substrate at initial implantation (for example, after 1 to 7 days of implantation to a coronary artery) and during early periods (within one month after implantation). If the local corrosion occurs too quickly, a large amount of corrosion products accumulate. Therefore, endothelialization of the device is incomplete, and the risks of acute and sub-acute thrombosis are high. Some parts of the substrate may crack when corrosion is severe, and the device fails to provide effective support. Therefore, for an iron-based device including a degradable polyester, at present, a significant problem that needs to be addressed is to avoid local corrosion of the iron-based device at the initial and short-term periods after implantation so as to ensure safety and effectiveness of the iron-based device.